Metal hydrocarbon difluoramines and their preparation



1967 E. A. SCHMALL 3, 7

METAL HYDRQCARBON DIFLUORAMINES AND THEIR PREPARATION Filed Oct. 25. 1960 OUT LET TO VACUUM PUMP a 1 2 6 $14: 3 fi M FEED I 4 OXIDIZING v GAS FEED (REACTOR REACTANT Edwin A. Schmall Inventor By 1 2M7 fiM nited States Patent Ofiice 3,346,347 METAL HYDROCARBON DIFLUO AND THEIR PREPARATION Edwin A. Schmall, Springfield, N.J., assignor t Esso Research and Engineering Company, a corporation of Delaware Filed Oct. 25, 1960, Ser. No. 64,959 17 Claims. (Cl. 23-356) This invention relates to metal difiuoramine compounds and the preparation thereof. More particularly, this invention relates to the preparation of metal alkyl difluoramine compounds by a diffusion process.

For a long time those skilled in the propellant art have sought compounds that are strong oxidizing agents that could be used as monopropellants and as oxidizers in propellant compositions. In order to obtain efficient high energy propellants, attempts have been made to make compounds which contain difluoramine groups and which also contain metals such as aluminum, boron, lithium, and lithium-aluminum. This type of compound has not been made, heretofore, due to the explosions that generally occur when the necessary reactants are brought into contact. Early attempts to react fluoramine oxidizing agents with these metals resulted in the reduction of the amine to nitrogen, the formation of the metal fluorides and/or violent explosions.

An object of this invention is to make novel metal difluoramines. Another object of this invention is to utilize a diffusion technique to contact the fluoramine oxidizing agent with the liquid metal-hydrocarbon under controlled conditions so that explosions do not occur. Applicant has now found that compounds of the following formula M(R) NF may be obtained by contacting a metalhydrocarbon of the following formula MR with an oxidizing gas such as N F NF H and NF The valence of M is represented by m, and M is a member of the group comprising lithium, aluminum, boron, and lithium-aluminum.

The reactor is first flushed out with an insert gas such as helium and then charged with a metal-hydrocarbon. Communication between the reactor on a second vessel is closed and the latter is charged with the oxidizing gas to a pressure equal to or up to 200 mm. Hg less than the pressure in the reactor. A molar ratio of oxidizing gas to metal-hydrocarbon of :1 to 1:10 can be used. The means by which the two vessels are in communication is opened and the insert gas over the liquid metal-hydrocarbon flows into the vessel containing the oxidizing gas until the pressure between the two vessels becomes equalized. The oxidizing gas then slowly diffuses into the reactor and reacts with the liquid metal-hydrocarbon, at a temperature between 100 C. to +200 C. The reaction is continued for up to 20 days.

The method of the present invention is particularly useful for reacting strong oxidizing agents such as N F NF and NF H with metal-hydrocarbons wherein the metal is lithium, aluminum, boron and lithium-aluminum. A principal advantage of the process is that it allows slow diffusion of the oxidizing agent to the highly reactive metal-hydrocarbon so that the reaction can be carried out slowly, under controlled conditions, without an explosion occurring.

The accompanying drawing is a flow diagram of the process. The metal of the metal-hydrocarbon which can be used in accordance with applicants invention is selected from the group comprising aluminum, boron, lithium and lithium-aluminum. The hydrocarbon may be alkyl or carbocyclic. The alkyl groups containing 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, for example, methyl, ethyl, butyl, and pentyl can be used. Car- Patented Oct. 10, 1967 bocyclic compounds such as cycloalky, e. g., cyclopentane, cyclohexane, and aromatic compounds containing 6-12 carbon atoms, e.g., phenyl and naphthyl can also be used. It is to be understood that the metal may be substituted with hydrogen as Well as hydrocarbon groups. Specific compounds which come within the scope of applicants invention are lithium phenyl, aluminum triethyl, diethyl aluminum hydride, boron triethyl, boron tripentyl, dipentyl boron hydride, lithium aluminum hydride, lithium hydride, aluminum trihexyl, monoethyl aluminum hydride, aluminum trididecyl, aluminum triheptadecyl, etc. The metalhydrocarbon can be used in pure form or may be diluted with suitable inert liquid solvents or diluents. The solvents may be hydrocarbons or oxygenated solvents. Suitable solvents are monoglyme, diglyme, tetrahydrofuran, diethyl ether, pentane, hexane, heptane, decane, etc. The ratio of metal reactant to solvent can be 120.1 to 1:10 parts by weight. The solvent acts as a diluent and generally does not affect the reaction.

The oxidizing gas is selected from the group comprising N F HNF and NF The oxidizing agent can be used in pure form or diluted with an inert gas such as helium, nitrogen, argon, etc. The volume ratio of oxidizing agent to inert gas can be 1:0.1 to 1:10, and is not critical. The reaction is carried out under conditions at which the metal-hydrocarbon is in the liquid phase and the oxidizing agent is in a gas phase. While the preferred reaction temperatures are between 0 and 160 C., the temperature range can be from C. to 200 C. depending upon other factors, e.g., pressure and concentration of reactants. The reaction pressure is not critical, except that it is necessary that the initial pressures within the reactor and the vessel containing the oxidizing gas be the same or that the pressure of the oxidizing gas be up to 200 mm. Hg less than the pressure of the inert gas atmosphere over the liquid metal-hydrocarbon. The reaction is preferably carried out at about atmospheric pressure with the initial pressure of the oxidizing agent being the same or up to 50 mm. Hg less than the pressure in the reactor. With the pressures of the reactor and the vessel containing the oxidizing gas at the same pressure or with the vessel containing the oxidizing gas at a lower pressure, too rapid a contact between the oxidizing gas and the liquid metal-hydrocarbon is prevented.

The molar ratio of the oxidizing gas to the metal-hydrocarbon reactant can vary from 10:1 to 1:10. The selected ratio will depend upon the particular reactants and the conditions used. A molar ratio of oxidizing gas to reactant between 5:1 and 1:1 is preferred. The reaction is carried out for periods of up to 20 days, preferably for not more than 10 days, for example 1 to 5 days. The time it will take to complete the reaction will depend upon the particular reactants used and the temperature at which the reaction is carried out.

The reactor may be any suitable Vessel which is inert to the reactants, capable of being heated or cooled to the desired reaction temperature, and capable of withstanding the pressures used. The reactor is so constructed that it communicates with the vessel containing the charge of oxidizing agent by a means which may be opened and closed. An understanding of the various aspects of the invention may be added by referring to the accompanying drawing which is a preferred embodiment of the invention. The drawing is in the nature of a flow diagram and various specific pieces of equipment have not been shown.

Referring now to the drawing, a liquid metal alkyl is charged to reactor 1, which has been previously flushed with helium, and which now contains a helium atmosphere at about atmospheric pressure, through inlet line 8 by opening valve 7. 'Valve 7, and valve 2 in line 3 are then closed. Reactant vessel 4 and line 3 are evacuated through outlet line 1%) with valve 9 open. Valve 9 is then closed and vessel 4 is filled with N F to a pressure equal to the pressure in reactor 1 or to a pressure up to 60 mm. Hg less than the pressure in reactor 1, through line 5 by opening valve 6. Valve 6 is then closed and valve 2 is opened, and the pressure between reactor 1 and vessel 4 becomes equalized. Where vessel 4 is maintained at a pressure below the pressure of the inert gas atmosphere in reactor 1, and when valve 2 is opened, the inert gas from reactor 1 flows into vessel 4 preventing a rapid contact of the oxidizing agent in vessel 4 and the metal alkyl in reactor 1. After the pressure between vessels 1 and 4 is equalized (or if they were the same initially), the oxidizing agent is gradually brought into contact with the metal alkyl by diffusion. During the reaction the metal-alkyl is agitated by a metal stirrer (not shown). The reaction is terminated after 1 to 5 days by replacing the oxidizing gas phase with nitrogen. The product is removed from the reactor, washed several times with pentane, dried and collected on a filter.

The invention is further illustrated by various runs reported in the following examples.

Example 1 The reactor was charged with 2 grams of concentrated triethyl aluminum in an inert atmosphere of helium and stirred by a magnetic stirrer. The reactor was at about atmospheric pressure and maintained at a temperature of 25 C. The reactant vessel was first evacuated and then charged with 500 cc. of N F at a pressure of about 700 mm. Hg which was 20 to 60 mm. less than the pressure in the reactor. The valve in the line connecting the two vessels was opened and some helium from the reactor flowed into the reactant vessel containing the N F gas. This procedure precluded any violent reaction between the N F and the triethyl aluminum in the reactor. After the pressure between the two vessels became equalized, the N F slowly diflused into the reactor containing the triethyl aluminum. The triethyl aluminum was slowly converted from a colorless liquid to a viscous glass. The pressure within the system generally increases during the reaction period. The reaction was terminated after 8 days by replacing the oxidizing agent with nitrogen. The glassy aluminum diethyl difluoramine product was mixed with pentane for several hours. The pentane was removed and the product collected on a filter and dried first by suction, then by high vacuum. On drying, the product was converted to a finely dispersed powder. The product (1.2 grams) was identified as aluminum diethyl difluoramine.

Example 2 The reactor was charged with 1.7 grams of triethyl aluminum which was then contacted with 400 cc.s of N F following the procedure of Example 1, except that the reaction vessel was maintained at a temperature of 75 to 80 C. Solid aluminum diethyl difluoramine (0.7 gram) was recovered. At the higher temperature, however, the reaction was completed in 3 days instead of 8 days.

Example 3 The process of Example 1 was carried out using aluminum triethyl and NF as the reactants. The reactor was charged with 0.5 gram of aluminum triethyl which was contacted with 450 cc.s of NF by diffusion at 100 C. and at about atmospheric pressure for 2 days. A solid product (0.08 gram) which was identified as aluminum diethyl difluoramine was recovered.

Example 4 The procedure of Example 1 was carried out in two additional runs using tripentyl boron as the metal-alkyl and tetrafiuorohydrazine as the oxidizing agent under the conditions listed with the following results.

Run 1 Run 2 B(C5H11)3, g 1. 0 2. 0 NzF cc 250 500 Temperature, C 75 75 Time, days 7 10 Product, g 0.7 1. 5

The product was identified as B(C H NF The analyses of the products obtained from Examples 1 and 4 are given in Table I.

The metal difluoramine compounds made in accordance with this invention find ready use as monopropellants, as oxidizing agents in rocket propellant compositions and as intermediates in making other useful compounds. These compounds may also be used as explosives, in explosive compositions, and as oxidizing and fluorinating agents. Specifically, aluminum diethyl difluoramine, boron diethyl difluoramine, boron dipentyl difluoramine and lithium difluoramine can be used as high energy components in solid rocket propellant compositions wherein a source of oxygen, e.g., nitroform, is included to convert the hydrocarbons to CO and/ or CO Other compounds coming within the scope of this invention are lithium aluminum hydride monodifluoramine, aluminum dihexyl difluoramine and boron dibutyl difluoramine.

It is not intended to restrict the present invention to the foregoing examples, but rather it should only be limited by the appended claims by which it is intended to claim all the novelty inherent in this invention.

What is claimed is:

1. A metal difluoramine compound of the following formula M(R), NF wherein M is metal selected from the group consisting of lithium, aluminum, boron, and lithium-aluminum, m is the valence of the metal, and R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, phenyl and naphthyl hydrocarbon groups containing 1 to 20 carbon atoms.

2. The composition of claim 1 wherein R is an alkyl group containing 1 to 6 carbon atoms.

3. The composition of claim 1 wherein R is an aromatic hydrocarbon group containing 6 to 12 carbon atoms.

4. Lithium difluoramine having the formula LiNF 5. Aluminum diethyl difluoramine having the formula Al(C2H5)2NF2.

6. Boron diethyl difluoramine having the formula 7. Boron dipentyl difluoramine having the formula B 5 11)2 2.-

8. Lithium aluminum hydride monodifiuoramine having the formula LiAlH NF 9. Aluminum dihexyl difluoramine having the formula 6 1a)2 2- 1d. Boron dibutyl difluoramine having the formula B (C 11 NF 11. A process of making metal difluoramine compounds of the following formula M(R). NF wherein M is metal selected from the group consisting of lithium, aluminum, boron, and lithium-aluminum, m is the valence of the metal, R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, phenyl and naphthyl hydrocarbon groups containing 1 to 20 carbon atoms, comprising reacting a compound of the formula M(R) with an oxidizing gas of the group consisting of N F HNF and NE; at a temperature of -100 C. to +200 C. at about atmospheric pressure for up to 20 days and recovering the resulting metal difiuoramine compound.

12. The process of claim 11 wherein R is an alkyl group containing 1 to 6 carbon atoms.

13. The process of claim 11 wherein R is an aromatic hydrocarbon group containing 6 to 12 carbon atoms.

14. The process of claim 11 wherein the compound of formula M(R) is aluminum triethyl and the oxidizing gas is N F 15. The process of claim 11 wherein the compound of formula M(R) is aluminum t-riethyl and the oxidizing gas is HNF 16. The process of claim 11 wherein the compound of formula M(R) is boron tripentyl and the oxidizing gas is NF 17. The process of claim 11 wherein the compound of the formula M(R). is lithium phenyl and the oxidizing gas is N F References Cited UNITED STATES PATENTS 3,294,495 12/1966 Lawton et a1. 23356 MILTON WEISSMAN, Primary Examiner. LEON D. ROSDOL, Examiner. 

1. A METAL DIFLUORAMINE COMPOUND OF THE FOLLOWING FORMULA M(R)M-1NF2 WHEREIN M IS METAL SELECTED FROM THE GROUP CONSISTING OF LITHIUM, ALUMINUM, BORON, AND LITHIUM-ALUMINUM, M IS THE VALENCE OF THE METAL, AND R IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL, CYCLOALKYL, PHENYL AND NAPHTHYL HYDROCARBON GROUPS CONTAINING 1 TO 20 CARBON ATOMS.
 11. A PROCESS OF MAKING METAL DIFLUORAMINE COMPOUNDS OF THE FOLLOWING FORMULA M(R)M-1NF2 WHEREIN M IS METAL SELECTED FROM THE GROUP CONSISTING OF LITHIUM, ALUMINUM, BORON, AND LITHIUM-ALUMINUM, M IS THE VALENCE OF THE METAL, R IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL, CYCLOALKYL, PHENYL AND NAPHTHYL HYDROCARBON GROUPS CONTAINING 1 TO 20 CARBON ATOMS, COMPRISING REACTING A COMPOUND OF THE FORMULA M(R)M WITH AN OXIDIZING GAS OF THE GROUP CONSISTING OF N2F4, HNF2 AND NF3 AT A TEMPERATURE OF -100*C. TO +200*C. AT ABOUT ATMOSPHERIC PRESSURE FOR UP TO 20 DAYS AND RECOVERING THE RESULTING METAL DIFLUORAMINE COMPOUND. 